Envelope for cathode ray tubes



Jan. 10, 1967 w. R. AIKEN ENVELOPE FOR CATHODE RAY TUBES Filed May 14, 1964 iii!- I iii!!! Q Q Q l Q l I l I INVENTOR. WI LIAM SS AIKEN United States Patent 3,297,188 ENVELOPE FOR CATHODE RAY TUBES William R. Aiken, M410 lldagdalena Ave, Los Altos Hilis, Calif. 94022 Filed May 14, 1964, Ser. No. 367,921 6 Claims. (Cl. 2202.1)

The present invention relates to the envelopes of cathode ray tubes, such as television tubes. Envelopes of this type are usually made from glass or a combination of glass and metal. The reason for this choice is that the materials must be impervious to the passage of air, and must not be subject to outgassing, i.e. the material must not contain moisture and/or gasses, such as air, that seep gradually into the interior of the envelope after it has been evacuated, and impair the vacuum. While glass is the preferred material for reasons of cost, it has the serious disadvantage that it is of low tensile strength. For this reason the walls of tube envelopes made from glass must be so designed that they are under a compressive force upon evacuation of the envelope. This makes it necessary to give the envelope a rounded configuration or to compose it from sections that are basically sphere segments. This approach made it possible to construct sturdy and relatively light glass envelopes for tubes of conventional design. However, it is not readily applicable to the flat cathode ray tubes known as the Kaiser- Aiken-ty-pe tubes whose envelopes are bounded by large and preferably fiat front and rear wall areas. \Vhen such envelopes are evacuated, the outer surfaces of the large spans constituted by their substantially fiat front and rear walls are under compression, but the inner surfaces of these walls are under tension, and the walls are therefore liable to break after evacuation unless they are made of exceptional thickness.

The present invention aims to lighten the weight and reduce the cost of envelopes for cathode ray tubes without sacrifice in their structural strength.

In particular, the present invention aims to provide an envelope for the Kaiser-Aiken type cathode ray tubes, that provides adequate tensile strength and yet is relatively light in weight.

The present invention also contemplates the use of low cost materials in the construction of tube envelopes, such as ceramic, cement-like and plastic materials because these materials lend themselves readily to forrning and are therefore instrumental in lowering the cost of the production process of the envelopes. Since these materials are known to be structurally weak and of a low tensile strength, it is a particular object of this invention to provide an envelope construction which makes use of such materials without sacrifice in the strength, safety and dependability of the resultant structure.

In the accompanying drawing:

FIGURE 1 is a perspective of an envelope embodying the invention, viewed from a point to the rear of the envelope;

FIGURE 2 is a vertical cross section through the envelope with some of the components of the assembled cathode ray tube indicated schematically in its interior; and

FIGURE 3 is a horizontal section through the envelope taken along line 33 of FIGURE 2 and viewed in the direction of the arrows associated with said line.

The exemplary envelope illustrated in the accompanying drawing is intended to form part of a so-called flat or compact cathode ray tube such as disclosed in my US. Patent 2,928,014, issued on March 8, 1960. It has basically the form of a shallow rectangular tray 6 that rests upon one of its narrow sides 8. To impart increased tensile strength to the walls of the envelope in spite of inherent low tensile strength of the materials employed in its construction, I provide a plurality of vertically equi-spaced horizontally extending ribs 10 on the surfaces of its walls except its picture area 12, i.e. a major area of its front wall 14, which commences as a rule at a level somewhat above its bottom wall 8. Additionally, a plurality of horizontally equi-spaced vertical strengthening ribs 18 may be provided on the surfaces of the envelope except its picture area 12, so that the surface of the envelope may have an appearance somewhat like a waffle iron, as best shown in FIGURE 1. In the embodiment of the invention illustrated in the accompanying drawing the ribs 16} and 18 are provided along the external surfaces of the envelope. It will be understood, however, that they may also be provided along the internal surfaces of the envelope, and may in fact be provided along both, its external and its internal surfaces.

As an added means for strengthening the walls of the envelope against tensile stresses, I embed reinforcing members into the walls of the envelope, except in the picture area 12 of the tube, such as vertically and/ or horizontally extending piano wires. The strengthening members may be located within the walls of the envelope or within the ribs 10 and 18, as indicated at 20 and 22 in FIG- URES 2 and 3.

In the event that ceramic, cement-like or plastic materials are employed in the construction of the envelope, the picture area 12 is formed by a separate sheet of plate glass that is secured to the adjacent edges of the remaining body portion of the envelope in a gas-tight manner and Which carries upon its inner surface a layer of phosphor 24. If the body portion of the envelope is made from ceramic or cement-like material, I prefer to secure the glass plate 12 to the body portion of the envelope by interposing strips of copper between the peripheral areas of the plate and the adjacent edges of the body portion, and subjecting the assembly to elevated temperatures until the glass has fused to the body portion through said strips of copper. Furthermore, if ceramic or cement-like materials are used in the construction of the body portion, it is necessary that they be provided with a gas-tight outer and/or inner coat. For this purpose the outer and/or inner surfaces of the body portion may be glazed in a manner well-known in the ceramic art, as schematically indicated at 26 in FIGURES 2 and 3 and as described in my copending patent application for an envelope for cathode ray tubes, filed this same date.

Tube envelopes constructed in the manner described above are of great tensile strength, withstand fully the strains exerted upon them, after evacuation, by the atmosphere, and are therefore safe to use even when made from materials of such poor tensile strength as pottery clay, concrete or plaster of Paris. Since these materials are inexpensive and can readily be formed into any desired shape, in fact, some of them may be cast into the desired shape and hardened at room temperature, envelopes made from these materials in the described manner combine economy with excellence in performance and durability.

The expression cement-like where used in the specification and claims is intended to refer to any material, organic or inorganic, which is capable of being cast and which will set after casting, such as the various types of pottery clay, concrete and plaster of Paris enumerated above.

While I have described my invention with the aid of certain embodiments thereof, it will be understood that the invention is not limited to the specific constructional details shown or described nor to the specific materials mentioned by way of example.

I claim:

1. A flat envelope for cathode ray tubes having a transparent picture area and areas containing metallic reinforcing members in the regions subject to tensile stress.

2. A fiat envelope for cathode ray tubes comprising a transparent picture area and areas provided with reinforcing ribs and containing reinforcing members in the regions subject to tensile stress.

3. A fiat envelope for cathode ray tubes comprising a transparent picture area and areas provided with externally located reinforcing ribs and containing reinforcing members adjacent the base of said ribs.

4. A flat envelope for cathode ray tubes consisting of a transparent picture area of glass and Walls of a materail of the group consisting of ceramic, cement-like and plastic materials, having strengthening ribs and containing strengthening wires in the regions subject to tensile stress.

5. A fiat envelope for cathode ray tubes comprising relatively spaced front and rear walls and side walls, said front wall having a transparent picture area of glass and the remaining area of said front wall and said rear and said side walls being made of a material of the group consisting of ceramic, cement like and plastic materials and having externally located sets of parallel reinforcing ribs disposed at right angles to each other.

6. A flat envelope for cathode ray tubes comprising References Cited by the Examiner UNITED STATES PATENTS 2,210,489 8/1940 Lemrnen et al. 22021 X 2,840,256 6/1958 Cobb 22071 2,969,162 1/1961 Stutske 2202.1 2,997,621 8/1961 Schlesinger 313-92 3,166,211 1/1965 Stel et al. 2202.1 3,207,936 9/1965 Wilbank et al. 220-21 X 3,223,273 12/1965 Thorington 2202.1

FOREIGN PATENTS 867,824 9/1941 France.

THERON E. CONDON, Primary Examiner. MARTHA L. RICE, Assistant Examiner. 

1. A FLAT ENVELOPE FOR CATHODE RAY TUBES HAVING A TRANSPARENT PICTURE AREA AND AREAS CONTAINING METALLIC REINFORCING MEMBERS IN THE REGIONS SUBJECT TO TENSILE STRESS. 